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Is a chocolate treat likely to increase the chance of my colleague developing cancer of the breast, and another recurrence of my own prostatic cancer? Will the butter on the hot-cross buns at Easter be more hazardous than chocolate eggs, and just how much did that steak increase the likelihood of my developing colorectal cancer? Would I have done better to have chosen guinea fowl, because one study indicated that where red meat increased the incidence of some gut cancers, white meat reduced it?These are some of the questions raised by research published last week by the Vasterbotten Intervention Project in Sweden. It studied the medical history of 64,500 men and women, and compared the incidence of cancer of the pancreas, skin, uterus and urinary tract with blood sugar levels.Part of the funding for the project was provided by the World Cancer Research Fund (WCRF). The project demonstrated a heightened risk for women but not for men. Unexpectedly, males with higher than average blood sugar levels were less likely to develop prostate cancer, but this difference was not clinically significant. A high-fat diet had previously been thought to be one of the factors that might increase the incidence of prostate cancer.The heightened risk posed by increased blood sugar levels was, however, significant for those women whose levels were in the top quarter of the league table. They had an appreciably greater chance of developing one of the four cancers than did those in the bottom quarter of the table. Why the blood sugar caused an increase in these four cancers is unexplained, though. Was it an effect of raised insulin levels and insulin resistance, or was it associated with obesity?The WCRF (UK) will publish its own more extensive study in November. This will be a follow-up to a similar but less rigorous examination of the statistics that were available and published in 1997. Rumour has it that the new report will not only extend existing knowledge, but has also detected differences in the emphasis that should be given to various known risk factors.